Laminate for protecting metals from corrosive gases

ABSTRACT

A corrosive gas resistant laminate comprises an outer polymer layer desirably containing a volatile corrosion inhibitor therein, a corrosion gas resistant barrier layer that can be a hydrophilic polymer, and a tie layer located between said outer and said barrier layers. The various laminates have improved transmission resistance with regard to corrosive gases such as oxygen, hydrogen sulfide, and halogen gases such as chlorine. The laminates can be used to protect metal during storage and transit.

CROSS REFERENCE

This is a division of U.S. application Ser. No. 12/927,986, filed Dec.1, 2010 for A LAMINATE FOR PROTECTING METALS FROM CORROSIVE GASES, whichis hereby fully incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a corrosive gas resistant barrierlaminate that resists penetration of corrosive gases such as oxygen,halogen gases, hydrogen sulfide, sulfur dioxide, HCl, Cl₂, and the like.The laminate comprises many different embodiments such as at least oneouter layer desirably containing at least one volatile corrosioninhibitor, at least one corrosive gas resistant barrier layer that canbe a hydrophilic polymer, and optionally one tie layer located betweenthe outer layer and said corrosive gas resistant barrier layer. Thelaminate when applied to a metal as a layer thereon or as a wrap such asa bag provides synergistic protection against the above noted corrosivegases.

BACKGROUND OF THE INVENTION

Heretofore, various polymers or polymers containing a volatile corrosioninhibitor therein, and optional antioxidants either within the polymeror within a separate polymer layer, have been utilized as gas barrierfilms as for oxygen, sulfur dioxide, and hydrogen sulfide. The prior artalso relates to various laminates that serve as a food wrap and containan ethylene-vinylalcohol layer therein. The following documentsrepresent a sampling of such prior art.

Various publications and patents relate to anti-corrosive material toprotect various substrates such as metals, conduits, and the like fromcorrosion. Such articles include WO Publication 97/49870, U.S. Pat. No.5,281,471, 5,855,975, 6,224,957, 6,316,520, 6,787,065, 7,261,839,7,270,775, and U.S. Publication 2009/0151598.

BluGuard-VCI™ relates to an Anti-Corrosion Barrier Lamination With VpCI®Technology (Vapor Phase Corrosion Inhibiting Technology) generally inthe form of a three-layer structure that sandwiches a foil barrier layerbetween an outer layer of clear PET and an inner sealant layer of VCIimpregnated film.

Mitsubishi Gas Chemical Company produces a polyamide MXD6 that is acrystalline polyamide resin produced through the polycondensation ofmeta-xylene diamine (MXDA) with adipic acid under Mitsubishi GasChemical's technology. This polyamide resin can be utilized as a gasbarrier film either alone or in combination with nylon, polyester, andthe like.

Prior art that generally relates to biodegradable anti-corrosivelaminates are set forth in U.S. Pat. Nos. 6,028,160, 6,156,929, and6,617,415. Laminates that generally serve as packaging or food wraps areset forth in U.S. Pat. Nos. 4,289,830, 7,087,277, and 7,588,820.

Laminates that serve to protect various electronic components orproducts are set forth in U.S. Pat. No. 7,112,169 and U.S. Publication2009/00151698.

Laminates that relate to absorbing harmful compounds are generally setforth in U.S. Publications 2004/0170780 and 2009/0041963.

SUMMARY OF THE INVENTION

A corrosive gas resistant laminate for protecting metal generallycomprises at least one outer layer that can optionally but desirablycontain a volatile corrosion inhibitor (VCI) therein, a corrosive gasresistant barrier layer with respect to the transfer of metal corrosivegases therethrough, and optionally but desirably a tie layer that bindsthe outer layer to the barrier layer. A five layer laminate contains aninner layer and an additional tie layer that, independently, can havethe same or different compositions (e.g. polymer) as the initial outerand tie layer. The corrosive gas resistant laminates of the presentinvention can also contain multiple outer, multiple tie, or multiplecorrosive gas barrier layers in various combinations so that the totalnumber of layers can vary greatly. Yet another embodiment of the presentinvention relates to the use of an outer layer and an inner layer with acorrosive gas resistant barrier layer therebetween and no separate tielayers. The various laminates of the present invention have been foundto yield synergistic results with respect to protecting metals fromcorrosive gases.

The present invention relates to a corrosive gas resistant laminate,comprising: at least one outer thermoplastic polymer layer optionallycomprising a VCI therein; at least one corrosive gas resistant barrierlayer; at least one optional tie layer that is compatible with saidouter layer and said barrier layer; and said laminate being capable ofprotecting metals against corrosion.

The present invention further relates to a corrosive gas resistantlaminate, comprising at least one corrosive gas resistant barrier layer;and at least one outer layer, said outer layer having at least one tielayer compound blended therein that is compatible with said outer layermaterial and said barrier layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a three layer corrosive gasresistant laminate;

FIG. 2 is a cross sectional view of a five layer corrosive gas resistantlaminate;

FIG. 3 is a cross-sectional view of a nine layer corrosive gas resistantlaminate containing an outer and a middle layer, four tie layers, twocorrosive gas resistant barrier layers, and one inner layer;

FIG. 4 is a cross sectional view of a three layer corrosive gasresistant laminate of the present invention containing an inner layer,an outer layer, with a corrosive gas resistant barrier layertherebetween; and

FIG. 5 is a cross sectional view of a three layer corrosive gasresistant laminate of the present invention wherein a corrosive gasresistant barrier layer is an outer layer.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention is shown in FIG. 1 whereincorrosive gas resistant laminate 10 is used for protecting metalarticles or substrates 100 from corrosion comprises outer layer 20 thatis bonded to corrosive gas resistant barrier layer 40 by tie layer 30.According to another embodiment of the present invention, a corrosivegas resistant barrier laminate 10A comprises five layers as shown inFIG. 2. Layer 120 is a top outer layer that is bonded to corrosive gasresistant barrier layer 140 by tie layer 130. An inner layer 160 is alsobonded to barrier layer 140 by second tie layer 150. Still anotherembodiment relates to a nine layer laminate 103 as shown in FIG. 3wherein outer layer 120 and inner layer 160, are connected respectivelyby tie layers 130 and 150 to top corrosive gas barrier layer 140A and tobottom corrosive gas barrier layer 1403. A third so-called middle outerlayer 145 is connected respectively by tie layer 130A to barrier layer140A and on its remaining side by tie layer 130B to barrier layer 1403.Yet another embodiment, is shown in FIG. 4 wherein three-layer laminate100 comprises outer layer 120 and an inner layer 160, that areseparately bonded to opposing sides of corrosive gas resistant barrierlayer 140. Optionally, a tie layer is blended into the outer and/orinner layer. These and other embodiments within the ambit of the presentinvention are described hereinbelow.

It is an aspect of the present invention that whether the laminate ofthe present invention has three layers, five layers, or any other numberof primary layers, each layer, independently, can comprise two or moresub layers, such as up to three, four, five, six, or eight total sublayers, wherein each sub layer, independently, can have the same ordifferent compositions. Thus, numerous combinations of sub layers existwith regard to forming an individual overall layer such as a outerlayer, a tie layer, or a corrosive gas resistant harrier layer.

The outer and inner layers of the multilayer films can be made out ofmany different types of polymer as set forth hereinbelow such aspolyester, nylon, and the like, with polyolefins being preferred due totheir low cost and good water and water vapor resistance and also sincethey comprise up to about 90% by weight of the total laminate weight.Still another aspect of the present invention is that the various outerand/or inner layers can be tailor made, depending upon the type ofprocessing equipment available, by a particular manufacturer to reduceconstruction expenses of the various laminates. For example, extrusionequipment can be utilized, or multilayer cast lines can be utilized, orblown multilayer lines can be used to make the corrosion gas resistantlaminates. Thus, inner and/or outer layer polymers are utilized thatare 1) suitable stable thermoplastic resins (petroleum or biobased)which can produce blown or cast multilayer film; and 2) that possess therequired physical properties, i.e. strength, puncture resistance, UVresistance, tear resistance, cost, temperature resistance and otherrequired barrier properties.

The properties of the inner and/or outer layer are desirably notaffected by the various corrosive gases and in a preferred embodimentcontain a volatile corrosion inhibitor (VCI). In addition to the VCI oras an alternative embodiment, the outer and/or inner layer can containvarious other functional additives such as various biocides, variousantistats, various flame-retardants, various colorants, and variousscavengers, or any combination thereof. These additives allow for thepreparation of a corrosive gas resistant laminate that can be tailormade to fit a variety of circumstances or situations as set forthhereinbelow. Should the outer or inner layer not effectively bonddirectly to the barrier layer, it is desirable to use a tie layer asnoted hereinabove. The tie layer has adhesive properties and can be awide range of materials such as an organic compound, for example aresin, or an inorganic compound, but desirably is a synthetic compoundsuch as one or more different polymers.

The one or more outer and/or inner layers comprise one or morethermoplastic polymers often having hydrophobic properties such as apolyolefin, e.g. polyethylene, low density polyethylene, high densitypolyethylene including high molecular weight and ultra high molecularweight polyethylene, polypropylene and copolymers thereof, copolymers ofpolyethylene including ethylene-ethyl acrylate copolymers andethylene-methyl acrylate copolymers; one or more polymers derived fromdienes such as copolymers of acrylonitrile-butadiene-styrene (ABS),copolymers of polybutadiene, or polychloroprene, and copolymers ofbutadiene and styrene; polystyrene or methyl methacrylate-styrene; oneor more halocarbon containing polymers or copolymers such aspolychlorotrifluoroethylene, polytetrafluoroethylene, fluorinatedethylene polypropylene copolymer, polyvinylchloride, polyvinylidenechloride, polyvinylidene fluoride, and blends of polyethylene andpolytetrafluoroethylene; heterochain thermoplastic such aspolyaryletherketone copolymers of melamine formaldehyde; variouspolysulfides; various polyphthalamides; thermoplastic polyurethanes;various polyamides such as Nylon 6-6, or 6-10; various polyesters suchas polyethylene terephthalate; or any combinations of the preceding.Preferred outer and/or inner layer polymers include polyolefins andcopolymers as well as derivatives thereof, and bio-source orpetroleum-based polyesters and polyamides. A highly preferred outerpolymer is polyethylene and the various low or high density variationsthereof since the same are strong, economical, have good corrosionresistance, and have good puncture resistance. The various polyethylenesare also preferred in situations where good water and/or water vaporresistance is desired as in humid environments since they haverelatively low water vapor transmission rates (WVTR). Other desirablelow WVTR polymers include hydrophobic-type polymers, other polyolefinsand various rubbers and thus the amount of any blended hydrophilicpolymers such as polyesters is kept low or avoided. That is the amountof any such hydrophilic polymers blended with a polyolefin type or apolymer derived from a diene is generally less than about 10 parts byweight, desirably less than about 5 parts by weight, desirably less thanabout 2 parts by weight, and very preferably nil, that is contains nohydrophilic compound per every 100 parts by weight of the outer and/orinner layer polymer.

The thickness of the total of all inner and outer layers is generallyfrom about 65% to about 93% of the total thickness of the corrosive gasresistant laminate. Thus, the thickness of an individual outer layer oran individual inner layer will vary depending upon the total number ofouter and inner layers within a laminate. With respect to a five layerlaminate, as set forth in FIG. 2, the thickness of the outer layer aswell as the thickness of the inner layer, independently, will be fromabout 0.8 to about 22 mils and desirably from about 1.0 to about 1.9mils. Of course, depending upon desired end use, the total thickness ofthe corrosive gas resistant laminate, regardless of the number of layerstherein, can vary greatly. Alternatively, the total weight of the innerand/or outer layers can range from about 65% to about 93% and desirablyfrom about 70% to about 90% by weight of the total weight of thecorrosive gas resistant laminate.

The above-noted outer and/or inner layer additives such as biocides,antistats, flame retardants, scavengers, and colorants are utilized toimprove specific properties of the laminate. The amounts of suchadditive will vary depending upon the effectiveness thereof as well asthe desired end result and such amounts are generally known to the artand to the literature, or can be readily determined.

Biocides can generally be any compounds that inhibit the growth or killvarious microorganisms such as bacteria, molds, fungi, and the like.Suitable biocides include various chlorinated hydrocarbons,organometallic compounds, halogen-releasing compounds, metallic salts,organic sulfur compounds, quaternary ammonium compounds, phenolics, zincpyrithione, and the like. Such biocides can be compounded as aconcentrate and added to inner and/or outer layer. Art example of aninorganic antimicrobial compound is RTP Company MC X122009, a silverpowder containing masterbatch, that possesses relatively high heatstability and low volatility. It reduces the chance of microbeadaptation and provides long lasting effectiveness. The Ag loading canvary from 0.10% to 1.0%. A biocide that is effective in combating bothfungi and bacteria is ABF® made by Akcros Chemicals America of NewBrunswick, N.J. that contains OBPA, i.e. oxybisphenoxarsine. Abactericide, example is Intercide® ZnP that contains zinc pyrithione. Afungicide example is Intercide IPBC, based upon 3-iodo-2-propynyl butylcarbamate. These two intercide compounds are made by Akcros ChemicalsAmerica.

Various antistat additives can be used and includeelectrically-conductive polymers such as compounds that migrate to thesurface of a plastic or polymer and modify its electrical properties,e.g. various fatty quaternary ammonium compounds, fatty amines, and thelike such as GMS (glycerol monostearate), ethoxylated fatty acid amines,and dimethanolamines, and the like. Other antistatic additives includehygroscopic compounds such as polyethylene glycols and the like. Theantistatic additives can also be generally classified as nonioniccompounds. Internal antistats have the advantage of providing a certainminimum level of static dissipation regardless of environmental humiditybecause the additives themselves are conductive. Other commonlyavailable antistats include conductive carbons, metalized fibers andconductive carbon fibers.

Flame retardant agents are known to the literature and to the art andgenerally include inorganic salts such as ammonium sulfamate, zincborate, antimony oxychloride, and the like. The amount of such additivesgenerally vary depending upon the end use and thus can range from about1 or 2 parts by weight to about 3 or about 10 parts by weight for every100 parts by weight of the inner or outer layer of polymers.

Examples of scavengers include various alkali metal silicates, zincoxide, and combinations thereof. The scavengers are desirably anhydrous,meaning that the outer layer or inner layer polymer composition is nothydrolyzed to more than 5 weight percent under conditions at which anobject to be protected is stored in the corrosive gas resistantlaminate. The amount of the anhydrous scavenger when utilized is fromabout 0.01 percent to about 5 percent by weight based upon the totalweight of the corrosive gas resistant outer or inner layer.

Various colorants or processing aids additives can be utilized in thelaminates of the present invention. The dyes and/or pigments areutilized to impart a desired color to any layer or the overall laminate.Suitable dyes that are known to the art and to the literature can beutilized such as titanium dioxide, carbon black, red iron oxide, and thelike. Processing aids include various lubricants, release agents, andfillers slip additives, and the like that are well known to the art andto the literature are also useful.

The volatile corrosion inhibitors (VCI's) of the present invention thatare preferably utilized in the outer and/or inner layers are known tothe art and to the literature and generally include various triazolesand derivatives thereof such as benzotriazole and tolytriazole; variousbenzoates such as ammonium benzoate and cyclohexylammonium benzoate;various salts of benzoic acid; various carbonates, various carbamates;various phosphates; various alkali metal molybdates such as sodiummolybdate, various dimolybdates such as ammonium dimolylbdate, variousamine molybdates such as aliphatic or aromatic amine having a total offrom about 3 to about 30 carbon atoms, or a salt thereof; and variousalkali dibasic acid salts such as set forth in U.S. Pat. Nos. 4,973,448;5,139,700; 5,715,945; 6,028,160; 6,156,929; 6,617,415; and 6,787,065,hereby fully incorporated by reference. Useful VCI's of the presentinvention preferably include various organic nitrites such asdicyclohexylammonium nitrite and triethanolammonium nitrite, or alkalimetal nitrites such as potassium nitrite with sodium nitrite beingpreferred. The VCI can be added to the inner and/or outer layer byvarious conventional methods such as by blending it with a meltedpolymer, e.g. polyethylene. The amount of VCI within these layers isgenerally from about 0.25 to about 10 parts by weight, desirably fromabout 0.3 to about 6.0 parts by weight, and preferably from about 0.4 toabout 3.0 parts by weight per 100 total parts by weight of the innerand/or outer polymer layers.

With respect to the various VCI components that have been set forthhereinabove, in order to limit the amount thereof that are released bythe outer and/or inner layer polymer over a specific period of time andform a coating on the metal to be protected against corrosion, such VCIcomponents can be blended with various structuring compounds comprisingat least one solid or pasty substance having a melting point range offrom about 40 to about 100° C. and preferably from about 50 to about 90°C., or a liquid substance that is capable of forming when mixed with amineral filler a solid or pasty combination. Examples of suitablestructural compounds, liquid substances, and mineral fillers are setforth in U.S. Pat. No. 6,787,065 which is hereby fully incorporated byreference and include various waxes such as carnauba wax, bees wax,paraffin wax, microcrystalline wax, petrolatum, polyethylene waxoxidized microcrystalline wax, and polyethylene glycol 4000, andcombinations thereof. The amount of the one or more VCI components isgenerally from about 1 to 90% and preferably from about 20 to about 60%by weight and the amount of the one or more structuring agents is fromabout 10 to about 99% by weight, and preferably from about 40 to about80% by weight based upon the total weight of all VCI compounds and allstructuring compounds.

Another group of vapor phase corrosion inhibitors of the presentinvention that can be utilized to protect a broad range of metals suchas iron, aluminum, copper, nickel, tin, chromium, zinc, magnesium, andalloys thereof as set forth in US Pub, 2009/0151598 are hereby fullyincorporated by reference, and generally comprise (1) at least one C₆ toC₁₂ aliphatic monocarboxylic acid, (2) at least one C₆ to C₁₂ aliphaticdicarboxylic acid, and at least one (3) primary aromatic amide.Preferably the composition also comprises at least one (4) aliphaticester of hydroxybenzoic acid such as 4-hydroxybenzoic acid, and/or atleast one (5) benzimidazole, especially a benzimidazole substituted onthe benzene ring. The amount of component (1) is from about 1 to about60% by weight, the amount of component (2) is from about 1 to about 40%by weight, the amount of the (3) component is from about 0.5 to about20% by weight, the amount of the (4) component is from about 0.5 toabout 20% by weight, and the amount of the (5) component is from about 5to about 20% by weight. When utilized, this hydrophobic composition willapply a thin protective layer or film on the metal substrate or articleto be protected. The amount of these inhibiting substances set forth inU.S. Patent Publication No. 2009/0151598 that can be utilized in theouter and/or inner layer is generally from about 0.25 to about 5.0 orabout 10 parts by weight and desirably from about 0.2 to about 2.0 partsby weight for every 100 parts by weight of the one or more outer and/orinner layer polymers.

The corrosive gas resistant barrier layers of the present invention canbe hydrophilic and include various polyamides and polyamide copolymerswith crystalline polyamides being preferred such as various MXD6 nylonsfrom Mitsubishi Gas Chemical Company, Inc. Amorphous polyamides, e.g.made by DuPont can also be utilized. Copolymers of polyamides can alsobe utilized such as Nylon 610 and 612. A preferred polyamide copolymeris Nylon MXD6 which is polycondensation of meta-xylene diamine (MXDA)with adipic acid. This nylon copolymer has been found to have superiorgas barrier properties such as with respect to oxygen and carbondioxide, low water absorption, a high glass transition temperature, hightensile and flexural strength and modulus as well as excellent gasbarrier properties. Blends of polyamides and polyamide copolymers can beutilized with other polymers such as polyvinyl alcohol orpolyethylene-vinyl alcohol. A blend of an amorphous nylon with apolyethylene-vinyl alcohol resin is Selar® PA 2072 made by DuPontwherein the amount of the amorphous nylon can generally range from about10.0% to about 60% and desirably from about 20.0% to about 40% by weightbased upon the total weight of the amorphous nylon and thepolyethylene-vinyl alcohol.

Other corrosive gas resistant barrier layers include polyvinyl acetateand copolymers thereof or blends thereof with another polymer.

Preferred barrier layer polymers also include polyvinyl alcohol orcopolymers thereof such as polyolefin-vinyl alcohol wherein the olefinhas from 2 to 6 carbon atoms, and blends thereof with other polymerssuch as ethylene or propylene can also be used. Examples of polyvinylalcohol polymers include Eval E® made by Kuraray of Japan, Eval F® alsomade by Kuraray of Japan, and Soarnol D® sold by Nippon Gohsei of Japan.Copolymers of polyvinyl alcohol with ethylene are highly preferred. Theamount of ethylene in the copolymer is generally from about 30 to about45 mole %, desirably from about 34 to about 42 mole %, and preferablyabout 36 to about 40 mole % with the vinyl alcohol mole content beingthe remaining, that is from about 55 mole % to about 70 mole %,desirably from about 58 to about 66 mole %, and preferably from about 60to about 64 mole %. A suitable ethylene-vinyl alcohol copolymer isSoarnol ET3808 made by Soarnus LLC that contains 38 mole % of ethyleneand 62 mole % of vinyl alcohol.

Another preferred corrosive gas resistant barrier layer is made fromcarbon monoxide copolymer or interpolymers with either vinyl alcoholhomopolymers or olefin-vinyl alcohol copolymers such as ethylene-vinylalcohol copolymers. Such polymers are set forth in WO 01/11470 which ishereby fully incorporated by reference with regard to all aspectsthereof including ratios and weight amounts of the ethylene-carbonmonoxide copolymer and the polyvinyl alcohol copolymer, and the like.

Another desired barrier layer material of the present invention ispolyvinylidene chloride and copolymers thereof with vinyl chloride,acrylonitrile, or acrylates, as for example a copolymer of vinylidenechloride and methyl acrylate such as XU 32019.L from Dow.

The above barrier materials minimize the permeation of oxygen, watervapor and odors. These barrier layer materials can be used in the designof multi-layer blown films or alternatively, can be extruded.

The corrosive gas barrier layer instead of preferably being one layercan be made of various sub-layers wherein each sub-layer, independently,can be of the same or a different polymer as those set forthhereinabove. The total thickness of a preferred single corrosive gasbarrier layer of a laminate as set forth in FIG. 2 will vary dependingupon the thickness of the overall laminate, but is generally from about0.1 to about 0.6 mil, and desirably from about 0.2 to about 0.4 mil, fora corrosive gas resistant barrier laminate having a total thickness ofabout 4 mils. Alternatively, the total weight of the corrosive gasresistant barrier layer can range from about 2 or 3 wt. % to about 8 or10 wt. % based upon the total weight of the laminate.

The corrosive gas resistant barrier layer of the present invention canoptionally but desirably contain small amounts of a phenol additive andpreferably an ortho-substituted phenol generally having a melting pointbelow about 200° C. While numerous phenol compounds exist as set forthin U.S. Pat. No. 4,289,830 hereby fully incorporated by reference, thefollowing compounds are desired, 2-hydroxy-4-octoxybenzophenone,2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, octyl3-(3′,5′-di-t-butyl-4′-hydroxy)phenyl propionate, 2(2′-hydroxy-3′,5′di-tert-amyl)phenyl-benzotriazole, tertiary butyl salicylate,t-butylhydroquinone, and any combination thereof. The amount of thephenol compound in the corrosion gas barrier layer such as a copolymerof ethylene and vinyl alcohol copolymer generally ranges from about 0.5to about 10, desirably from about 0.7 to about 5, and preferably fromabout 0.8 to about 2 or 3 parts by weight based upon 100 total parts byweight of the hydrophilic or corrosion gas resistant barrier layer.

A tie layer can be utilized to bond the corrosive gas barrier layer tothe outer and/or inner layer. Thus, the tie layer is desirablycompatible with the outer and/or inner layer as well as the barrierlayer. As used in this specification, “compatible” means that aparticulate layer will adhere or bond to an adjacent layer and noteasily separate therefrom. Thus, tie layer materials or polymers areutilized that readily adhere to an adjacent barrier layer as well as toan adjacent outer or inner layer. If the outer and/or inner layer is ahydrophobic layer such as polyethylene or a rubber, hydrophilic polymersare avoided for the tie layer inasmuch as they are incompatibletherewith. The tie layer can be a preferred single layer, or two moresublayers. Tie layers of the present invention are desirably polymersand include various acrylate and methacrylate polymers wherein the esterportion can contain from 1 to about 12 carbon atoms. Blends of thevarious acrylates with polyolefins can also be utilized. The tie layercan also comprise polymeric anhydride such as polymers of maleicanhydride optionally having a substituted alkyl group (e.g. C₁-C₁₀) or asubstituted aryl group or a substituted alkyl aromatic group with thealkyl having from 1 to about 5 carbon atoms. Modified polymers, e.g.copolymers of an anhydride or of maleic anhydride with olefins such asethylene or propylene, or with ethylene vinyl acetate, or with ethyleneacrylate can also be utilized.

Specific examples of tie layers include anhydride chemically modifiedpolyethylene such as Admer NF 908A (Mitsui Chemical), anhydridechemically modified low density polyethylene such as Bynell 4208(DuPont), or anhydride chemically modified linear low densitypolyethylene such as Plexar® PX3236 made by Equistar. These copolymersgenerally contain from about 30 to about 40 mole percent olefin. Ofcourse, generally any type of polyolefin can be utilized that ismodified by maleic anhydrides such as high density polyethylene, lowdensity polyethylene, etc.

The total thickness of each of the two single tie layers as set forth inFIG. 2, independently, is from about 0.1 to about 0.6 mils, anddesirably from about 0.2 to about 0.4 mils, based upon a corrosive gaslaminate having a total thickness of about 4 mils. Alternatively, thetotal weight of the one or more tie layers can be from about 5 to about20%, and desirably from about 7% to about 18% by weight based upon thetotal weight of the corrosive gas resistant laminate.

According to another embodiment of the present invention, while the tielayer can generally be a separate layer as shown in the embodiment ofFIGS. 1, 2, and 3, it can be blended, as by calendering or extruding,with the inner and/or outer layers 20, 40, 120, 145, or 160 of FIGS. 1,2, and 3. That is, in order to reduce the number of processingoperations, the components of the inner/outer layer and the tie layercan be melt blended to form generally one uniform or homogeneousouter-tie layer. In this situation, the embodiment of FIG. 1 would onlyhave two layers, the blended outer layer 20 and the barrier layer 40,whereas in the embodiment of FIG. 2 would have only three layers, i.e.outer layer 120 and inner layer 160 separated by an intermediatecorrosion gas resistant barrier layer 140. The embodiment of FIG. 2wherein the tie layer is blended with the outer and the inner layer isshown in FIG. 4. Alternatively, the embodiment of FIG. 4 need notcontain any tie layer blended therein so long as the inner and outerlayer is compatible with barrier layer 140, but the same is generallynot preferred.

While desirably and preferably the outer and/or inner layers are locatedrespectively on the outer side of the laminate or on the inner or metalfacing side of the laminate, the corrosive gas resistant barrier layercan be located on the outside of the laminate with an inner layer beinglocated on the side of the laminate that is adjacent, contacts, orspaced apart from a metal object or article to be protected againstcorrosive gases. Such an embodiment is shown in FIG. 5. FIG. 5 is thusrepresentative of the corrosion gas resistant laminate of the presentinvention wherein the one or more layers of the corrosive gas resistantbarrier is located on the outside of the laminate with one or more innerpolymer layers located on the inside of the laminate. As with the aboveembodiments, the use of a tie layer is optionally, but generallydesired. The tie layer can be one or more separate layers 130 as shownin FIG. 5, or the tie layer can be blended with inner layer 160. Theembodiment of FIG. 5 is generally not desired since it is preferred tohave a polymeric water resistant layer located on the outside of thelaminate with the barrier layer desirably located adjacent to or incontact with the metal part to be protected in FIG. 1. With regard tothe thicknesses of the various layers of the embodiment of FIG. 5, theyare as set forth below. That is, the total thickness of the one or moreinner layers is by far the thickest amount of a laminate, with the totalof one or more corrosive gas resistant barrier outer layer being verythin in comparison as is the one or more tie layers based upon the totalthickness of the corrosive gas resistant laminate.

An alternative aspect of the present invention that in addition to thethree layer embodiment of FIG. 1 or the five layer embodiment of FIG. 2,numerous other embodiments exist that contain one or more additionalinner and/or outer layers, or one or more additional corrosive gasresistant barrier layers, and/or one or more additional tie layersdesirably located between the additional inner and/or outer layers andthe additional corrosive gas barrier layer. In such embodiments, theso-called outer layer can reside within the laminate, e.g. a middlelayer and not be located on an external surface thereof; see FIG. 3.Also, the embodiments of FIGS. 1 and 2 can, independently, contain oneor more additional inner and/or outer layers that are bound by a tielayer to an adjacent barrier layer or, alternatively, one or morehydrophilic or barrier layers that are bound desirably by a tie layer toan adjacent outer or inner layer. Thus, the number of so-called laminatepossibilities or embodiments is exceedingly large. For example, thetotal number of laminate layers can range up to about 8, up to about 10,or up to about 15, and so forth. It is further noted that in all ofthese embodiments the additional one or more outer and/or inner layers,one or more tie layers, and/or one or more corrosion gas resistantbarrier layers can independently, be the same or different type ofcompound or polymer, respectively, as any other outer and/or innerlayer, tie layer, or corrosive gas barrier layer.

As a specific example of a laminate embodiment of the present invention,reference is made to FIG. 2. Outer layer 120 is made of polyethylene andis approximately 40% by weight of the total weight of the five layerlaminate. Tie layer 130 is an ethylene-anhydride copolymer, or anethylene chemically modified anhydride copolymer and is approximately 6%by weight of the total laminate weight. Center or barrier layer 140 ispolyethylene-vinyl alcohol copolymer containing about 30 to about 40% byweight of ethylene repeat units therein. The barrier layer isapproximately 6% by weight of the total weight of the laminate. Tielayer 150 is the same type of polymer of tie layer 130 and also isapproximately 6% by weight of the total weight of the laminate, andinner layer 160 is a polyethylene layer and is approximately 40% byweight of the total weight of the laminate. With regard to outer layer120, it preferably contains about 2% by weight of a VCI that is e.g.sodium nitrite.

With respect to additives, a flame retardant such as decabromodiphenylether can be used in the inner and/or outer layers 160 and 120. Theouter layer 120 can contain a colorant as well as an antistat such asglycerol monostearate. Optional conductive fillers can also be containedin outer layer 120 that serve as an antistat agent such as Ampacet101140. Additionally, an antimicrobial or biocide agent such asMCX122009 can be utilized that is available from RTP Company of Winona,Minn., that contains silver.

Inner layer 160 can also contain a VCI, a flame retardant, a colorant,and a scavenger such as noted above.

The overall thickness of the various corrosive gas resistant laminatesof the present invention can vary largely depending upon the substrateor article it is to cover, wrap, contain, etc., but generally can rangefrom about 0.6 mil to about 10.0 mil, desirably from about 0.8 mil toabout 6.0 mil, and preferably from about 1.0 mil to about 5.0 mils.Based upon a total laminate thickness of 100%, the total thickness ofthe one or more outer and/or inner layers is by far the largest rangingfrom about 65% to about 92%, desirably from about 70% to about 90% andpreferably from about 80% to about 85%. The total thickness of one ormore tie layers is from about 3% or 5% to about 20%, desirably fromabout 7% to about 18% and preferably from about 9% to about 15%. Thetotal thickness of the one or more barrier layers is from about 2% toabout 15%, desirably from about 3% to about 10%, and preferably fromabout 4% to about 8%. When the tie layer compounds are blended witheither the inner and/or outer one or more layers, the total thickness ofthe blended outer and/or inner layers is from about 75% to about 98%,desirably from about 80% to about 97% and preferably from about 90% toabout 96% based upon the total thickness of the laminate, with thedifference being the total thickness of the one or more barrier layers.

The corrosive gas resistant laminates of the present invention such asset forth in FIGS. 1, 2, 3, and 4 comprise one or more polymers thatresist the penetration of corrosive gases therethrough. Corrosive gasesinclude oxygen, halogen gases such as chlorine and bromine, hydrogensulfide, sulfur dioxide, HCl vapors, and the like. Metals that can beprotected by the corrosive gas resistant laminates of the presentinvention include iron, steel, aluminum, copper, nickel, tin, zinc,chromium, magnesium, silver, and the like, as well as alloys thereof.The corrosive gas resistant laminates of the present inventionunexpectedly have large improvements with regard to resistingpenetration of corrosive gases therethrough. For example, the laminatesgenerally exhibit a penetration of about 10% or less, desirably about 5%or less, and preferably about 1% or about 0.1% or less with respect tovarious corrosive gases as that compared to plain polyethylene of equalthickness with respect to permeation per unit, time, and area. Indifferent terms, the corrosive gas resistant laminates of the presentinvention have unexpected and synergistic reductions with respect tooxygen transmission rates of less than about 1.0, desirably less thanabout 0.5 and preferably less than about 0.1 or less than about 0.05cc/100 in²/day. With respect to H₂S permeation transmission rates thevalue was less than about 200, desirably less than about 100, andpreferably less than about 50 cc/100 m²/day.

An important aspect of the present invention is that the variouspolymers utilized either in the inner and/or outer layers, the tielayers, and the corrosive gas barrier layers do not decompose and do notpermit moisture and/or the corrosive gases to attack the metal. Thus,the laminates of the present invention are generally free ofbiodegradable polymers such as various polyesters that are known to theart and to the literature, for example polylactate. That is, if thelaminates do contain biodegradable polymers, they are utilized in smallamounts such as less than about 5 parts by weight, desirably less thanabout 2 parts by weight, and preferably be nil, that is the individuallayers are free and do not contain any biodegradable polymers thereinbased upon 100 total parts by weight of the total laminate weight.

Fillers are generally not desired especially those that reduce theelongation of the laminates since the same can result in formation ofcracks, tears, cuts, etc., that reduce the resistance to the penetrationof corrosive gases and can lead to openings that will readily permit thecorrosive gases to attack the various metals. Mineral fillers such asclays, chalks, carbonates, talcs, nano-clays, silica, and the like arethus avoided. That is, the various individual layers of the laminatecontain generally less than about 5 parts by weight, desirably less thanabout 2 parts by weight, and preferably are free of, i.e. contain noparts by weight of any such fillers per 100 parts by weight of totalpolymers in the laminate.

The preparation of the corrosive gas resistant laminates of the presentinvention can generally utilize commercial methods, for examplecoextrusion, calendering, and utilize commercial blown multilayerequipment or cast multilayer equipment, and the like. Two such methodsare set forth as follows.

The polymers or resins of the outer and/or inner layers includingoptional tie layer components therein are added to a gravimetricadditive feeder. Such polymers, as noted above, include low densitypolyethylene, polypropylene, high density polyethylene and the like.These polymers can be fed into existing material streams or combinedwith a weight throughput monitor hopper. This process ensures even layerthicknesses. The screw speed is controlled via a weight reduction of theweighing hopper.

Additional optional additives such as Vas, antiblock, antisat,hydrophobic, colorants, processing aids, are combined by using eithervolumetric or weight loss feeding gravimetric techniques.Microprocessors are used to monitor the amount of material fed intomixing chambers.

A central blending station was used to pre-blend additives and resins.These resins and additives are accurately weighed and added to aspinning cylinder with mixing blades to uniformly distribute theadditives and polymers.

With regard to a co-extrusion process, the various outer and/or innerlayers as well as the optional tie adhesive layer compounds can bepre-blended and added to the gravimetric feeders that feed the extruderswhich produce the inner and outer layers. Barrier resin or polymers areadded to the core or middle extruder. The extruders delivered a steadyvolumetric throughput of different viscous liquids to a single extrusiondie. This process welds together the various layers by keeping themseparate. The layer thicknesses are controlled by the speed andindividual extruders delivering the material.

With respect to a general blown film extrusion process, the measuredouter and/or inner polymers or resins are introduced into the extruder.The melted (liquid) material is pushed (pumped) under continuouspressure, through a circular die to form a thin walled tube. Air isintroduced in the middle of the die to blow the tube. The film is cooledby using an air ring mounted at the top of the die. The blown film tubeis flattened through nip rollers and forms a lay flat tube which passesthrough rollers. Various tubing or sheeting forms can be converted intobags by heat sealing across the width of the film. Converted bags can beperforated on a roll or individually cut.

The present invention will be better understood by reference to thefollowing examples which serve to illustrate, but not to limit thepresent invention.

Two Controls were prepared as well as two Examples according to thepresent invention. Control 1 merely related to a 100% low densitypolyethylene film having a total thickness of 4 mils. Control 2 utilizeda commercial product, that is. Zerust® made by NTIC of Circle Pines,Minn., also having a total thickness of 4 mils. Control 2 was a 100% lowdensity polyethylene layer but also contained approximately 0.5 weightpercent of a volatile corrosion inhibitor, i.e. sodium nitrite andapproximately 0.5 wt. % of butylated hydroxy toluene, (BHT). Example 1was a five layer laminate of the present invention similar to that shownin FIG. 2 containing as the tie layers a copolymer of ethylene-maleicanhydride and as the corrosive gas barrier layer a copolymer ofethylene-vinyl alcohol. The total thickness of Example 1 was 4 mils andit did not, contain any volatile corrosion inhibitor. Example 2 was alaminate of the present invention essentially identical to that ofExample 1 except that one or both of the outer hydrophobic layers eachcontained approximately 0.5% by weight of sodium nitrite VCI. Adescription of the layers of the two Controls and two Examples are setforth in Table 1.

TABLE 1 Type of Layer Composition Thickness Control 1 Hydrophobic 100%low density polyethylene 4 mil layer Control 2 Hydrophobic 100% lowdensity polyethylene 4 mil layer 0.5 wt. % sodium nitrite 0.5 wt. % BHT(2,6-T-butyl-4- methyl phenol) (an antioxidant) Example 1 Outer layer100% low density polyethylene 41.0% Tie Layer Ethylene-anhydridecopolymer 6.0% Plexar ® PX3236 Corrosive Ethylene-vinyl alcohol 6.0%Resistant Gas copolymer (38 mole %) Barrier Layer (62 mole %) Tie Layerethylene-anhydride copolymer 6.0% Plexar ® PX3236 Inner Layer 100% lowdensity polyethylene 41.0% Example 2 Hydrophobic 100% low densitypolyethylene 41.0% layer   0.5 wt. % of sodium nitrite Tie Layerethylene-anhydride copolymer 6.0% Plexar ® PX3236 CorrosiveEthylene-vinyl alcohol 6.0% Resistant Gas copolymer (38 mole %) BarrierLayer (62 mole %) Tie Layer ethylene-anhydride copolymer 6.0% Plexar ®PX3236 Hydrophobic 100% low density polyethylene 41.0% Layer Totalthickness of Examples 1 and 2 was 4 mil.

The above laminate of Control 1 and 2, and Examples 1 and 2 were testedwith respect to oxygen as the corrosion gas as follows:

TABLE 2 Test Conditions: Test Gas Oxygen Test Gas Concentration 100% O₂Test Gas Humidity 90% RH Test Gas Pressure 760 mmHg Test Temperature23.0 (° C.) 73.4 (° F.) Carrier Gas 98% N₂, 2% H₂ Carrier Gas Humidity0% RHTest Results:

Oxygen Transmission Rate Sample Identification cc/(100 in²/day) 100%LDPE (Control) Example 1 122 Oxygen Barrier Example 1 0.0239 OxygenBarrier Example 2 0.0199

The above laminates were analyzed on a MOCON Oxtran 2/21 instrument. Thetest standards that were utilized include ASTM D-3985, ASTM F-1927; DIN53380, JS K-7126 and ISO CD 15105-2.

As apparent from Table 2, the transmission rate of oxygen with respectto Control 1, low density polyethylene was very high, i.e. 122. Incontrast thereto, Example 1 was a very effective corrosion gas resistantlaminate having an oxygen transmission rate of 0.0239 whereas Example 2had an oxygen transmission rate of 0.0199. Thus, the laminates of thepresent invention resulted in an unexpected and synergistic decrease inthe transmission rate of oxygen through the laminates of at least 5,000!

The above four laminates as set forth in Table 1 were also tested withrespect to hydrogen sulfide as the corrosion gas as follows:

Test Procedure

Films were stretched over a 60 cc Teflon jar. The center portion of thejar cap was removed so the film would be exposed to the outsideenvironment. The 60 cc Teflon jar has an inlet and outlet tube attachedto the sides. The corrosion gases, H₂S was connected to the tubesallowing a gas flow of 10 cc/min to go in and out of the jar on acontinuous basis. The Teflon jar was placed inside an outer vessel andsealed. As the gases permeated through the laminate they were capturedin the outer chamber having a probe located therein. The SPME (metaloxide coated silica fibers) located within the probe was exposed for 10minutes to the headspace and then injected into a GC inlet for areacount comparison to a known concentration standard. For hydrogen sulfidepermeation values two connectors were added to the top of the outervessel. One connector was attached to an Arizona Instrument Jerome 6314H2S analyzer. As the Jerome pulled a sample from the headspace volumefor analysis, this volume was replaced by allowing clean air filteredthrough a carbon bed to be drawn back into the vessel. The headspace wasstirred prior to sampling to ensure a uniform sample.

Test Results

The noted 4 different laminates were tested with regard to hydrogendisulfide penetration over various periods of time and the resultsthereof are set forth in Table 3.

TABLE 3 Permeation Exposure Concentration Time ppm H₂S Gasconcentration: 100 ppm H₂S Control 1 Start  0 min BDL  16 hrs 0.16  24hrs 10 min 1.10  40 hrs 40 min 0.70  51 hrs 55 min 0.89 195 hrs 50 min0.92 205 hrs 5 min 0.98 226 hrs 20 min 1.50 245 hrs 55 min 1.80 249 hrs55 min 1.50 269 hrs 45 min 1.30 273 hrs 30 min 1.70 Gas concentration:100 ppm H₂S Control 2 Start  0 min BDL  16 hrs 0.09  24 hrs 15 min 0.11 40 hrs 35 min 0.21  52 hrs 0.53 195 hrs 55 min 0.67 205 hrs 0.69 226hrs 10 min 0.98 246 hrs 1.10 250 hrs 10 min 1.20 269 hrs 55 min 1.15 273hrs 50 min 1.15 Gas concentration: 100 ppm H₂S Example 1 Start  0 minBDL  16 hrs 0.004  24 hrs 0.004  40 hrs 50 min 0.000  51 hrs 45 min0.006 195 hrs 45 min 0.004 205 hrs 15 min 0.020 226 hrs 15 min 0.017 245hrs 15 min 0.018 249 hrs 45 min 0.015 269 hrs 30 min 0.019 272 hrs 30min 0.017 Gas concentration: 100 ppm H₂S Example 2 Start  0 min BDL  16hrs BDL  24 hrs 5 min BDL  40 hrs 45 min BDL  51 hrs 50 min BDL 196 hrsBDL 205 hrs 10 min 0.001 226 hrs 30 min 0.001 245 hrs 50 min BDL 250 hrsBDL 269 hrs 50 min BDL 273 hrs 35 min BDL Film Number H₂S valuePermeation Rate Control 1 1.7 ppm 5,712 cc/m²/day Control 2 1.15 3,864cc/m²/day Example 1 0.017 57 cc/m²/day Example 2 BDL BDL (BDL meansbelow detectable limits)

As apparent from the above table, the laminates of the presentinvention, i.e. Examples 1 and 2, gave unexpected and synergisticimprovements with regard to the reduction of hydrogen sulfide gaspenetration as well as reduction of permeation rates through thelaminates in comparison to the Controls.

The same two Controls and the same two Examples a set forth in Table 1were tested with regard to permeation by chlorine gas in nitrogen. Whentested in the manner as set forth above with respect to the oxygenpermeation test, results were obtained as set forth in Table 4. Briefly,the test method related to films being stretched over a 60 cc Teflonjar. The center portion of the jar cap was removed so the film would beexposed to the outside environment. The 60 cc Teflon jar has an inletand outlet tube attached to the sides. The challenge gas, chlorine, wasconnected to the tubes allowing a gas flow of 15 cc/min to go in and outof the jar on a continuous basis.

The Teflon jar was placed inside an outer vessel and sealed. As thechallenged compounds permeated through the membrane they were capturedin the outer chamber.

To determine permeation values a Drager Tube, p/n 6728411, was insertedinto the headspace area of the outer vessel. The Drager tube wasspecifically made to detect chlorine gas as a concentration of 0-5 ppm.As the sample pump drew air out of the outer vessel the volume wasreplaced by allowing clean air filtered through a carbon bed to be drawnback into the vessel.

The headspace was stirred prior to sampling to ensure a uniform sample.

TABLE 4 Break- Equili- Total CI through bration ppm Dilu- Run ppmV/m²/time time Vol. tion Time day Con- 816 hrs. 864 hrs 0.25 ppm 1120 cc 1032hrs  0.025 trol 1 Vol. Con- 180 hrs. 227 hrs  0.3 ppm 1120 cc 984 hrs0.12 trol 2 Vol Exam- BDL BDL BDL 1120 cc 984 hrs BDL ple 1 Exam- BDLBDL BDL  970 cc 720 hrs BDL ple 2

The following eight examples were made and tested with respect to oxygenpermeation. Examples 3, 7, and 9 did not contain any VCI additivestherein, e.g. in the outer or inner layer, but the remaining examples,i.e. 4-6 and 8 and 10 did contain sodium nitrite as a VCI in the outerlayer. The results of the oxygen permeability test with regard toExamples 3-10 were very low oxygen transmission rates, with thetransmission rates of examples 4-6 and 8 and 10 containing a VCI thereinhaving slightly lower oxygen transmission rates than Examples 3, 7, and9 that contained no VIC. The actual oxygen transmission rates were verysimilar to that set, forth in Table 2 with respect to Examples 1 and 2.Thus, once again dramatically reduced and synergistic results wereobtained with regard to the corrosive gas resistant laminates of thepresent invention.

Example 3

A three layer corrosive gas resistant laminate having no VCI additives.(FIG. 4).

A three layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a low linear low density polyethylene resin, e.g.Exxon 1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, e.g. Equistar Plexar PX3236.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, i.e. Equistar Plexar PX3236.

Example 4

A three layer corrosive gas resistant laminate having VCI additive(s)added to the inner layer (FIG. 4).

A three layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series blended with an extrudable tie layer resin anhydridemodified LLDPE resin, e.g. Equistar Plexar 3236.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, i.e. Equistar Plexar PX3236, and sodium nitrite.

Example 5

A three layer corrosive gas resistant laminate having VCI additive(s)added to the outer and inner layers (FIG. 4).

A three layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, e.g. Equistar Plexar 3236, and containing sodiumnitrite.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, i.e. Equistar Plexar PX3236, and containing sodiumnitrite.

Example 6

A three layer corrosive gas resistant laminate having VCI additive(s)added to the outer and inner layers (FIG. 4).

A three layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, e.g. Equistar Plexar 3236, and containing sodiumnitrite.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series, blended with an extrudable tie layer resin anhydridemodified LLDPE resin, i.e. Equistar Plexar PX3236, and containing sodiumnitrite.

Example 7

A five layer corrosive gas resistant laminate having no VCI additive(s)therein (FIG. 2).

A five layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series.

An extrudable tie layer resin anhydride modified LLDPE resin, e.g.Equistar Plexar 3236.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An extrudable tie layer resin anhydride modified LLDPE resin, i.e.Equistar Plexar PX3236.

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series.

Example 8

A five layer corrosive gas resistant laminate having VCI additive(s)added to the inner layer (FIG. 2).

A five layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series.

An extrudable tie layer resin anhydride modified LLDPE resin, e.g.Equistar Plexar 3236.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An extrudable tie layer resin anhydride modified LLDPE resin, i.e.Equistar Plexar PX3236.

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series, and sodium nitrite.

Example 9

A five layer corrosive gas resistant laminate having no VCI additive(s)therein (FIG. 2).

A five layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series.

An extrudable tie layer resin anhydride modified LLDPE resin, e.Equistar Plexar 3236.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An extrudable tie layer resin anhydride modified LLDPE resin, i.e.Equistar Plexar PX3236.

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series.

Example 10

A five layer corrosive gas resistant laminate having VCI additive(s) inthe inner and outer layers (FIG. 2).

A five layer tube was coextruded to form a 4 mil film. The tubingcomprised:

An outer layer of a linear low density polyethylene resin, e.g. Exxon1001 series, and sodium nitrite.

An extrudable tie layer resin anhydride modified LLDPE resin, e.g.Equistar Plexar 3236.

A barrier layer of an ethylene vinyl alcohol copolymer, e.g. ET3803Soarnol (38% mol % content).

An extrudable tie layer resin anhydride modified LLDPE resin, EquistarPlexar PX3236.

An inner layer of a linear low density polyethylene resin, e.g. Exxon1001 series, and sodium nitrite.

As noted above, each of Examples 3-10 gave surprisingly and synergisticlow oxygen permeability values, similar to the values set forth inExamples 1 and 2 of Table 2.

The corrosive gas resistant laminates of the present invention can beutilized wherever metals are desired to be protected against corrosivegases. Thus, laminates can be utilized as wraps, protective covers,enclosures, and the like with respect to various metals and alloys. Enduses include the protection of various automotive parts and components,various machine, automotive parts and components, various marine partsand components, as well as numerous different types of electronicdevices as for example printed circuits, circuit hoards, unpopulatedboards, memory discs such as silver plated memory discs, and the like.Various metals per se as in the form as ingots, bars, chips, powder andthe like can also be protected by the laminates of the presentinvention. Still other uses relate to the protection of various militaryand aerospace alloys and components such as various magnesium alloyparts, coils, and the like. Other military and aerospace end usesinclude the protection of various airplane components such as landinggears, engine components, body and fuselage components, various wingcomponents, and other military items such as artillery and riflecomponents, control modules, and the like.

Since as noted above, the purpose of the corrosive gas resistantlaminates of the present invention is to protect various substrates,that is metals from corrosion and since the various layers, particularlythe outer layer contains various functional additives therein such asvolatile corrosion inhibitors, biocides, flame-retardants, and the like,it is imperative that the laminates of the present invention not beutilized to protect various foods such as grains, vegetables, fruits,dairy products, meats, and fish. Such use can be detrimental theretoparticularly to persons consuming such foods. Thus, the laminates arenot used as food wraps, packaging, bagging, or any other similarfunction with respect to foods and medicines.

While in accordance with the patent statutes the best mode and preferredembodiment have been set forth, the scope of the invention is notintended to be limited thereto, but only by the scope of the attachedclaims.

What is claimed is:
 1. A corrosive gas resistant laminate, comprising: alaminate capable of wrapping and forming a closed space about a metalsurface and capable of preventing metal corrosive gases comprising H₂S,SO₂, and halogen gases from corroding said metal surface, and whereinsaid laminate is not utilizable as a food wrap; said laminatecomprising: at least one outer thermoplastic polymer layer comprising aVCI; at least one corrosive gas resistant barrier layer; at least onetie layer that is compatible with said outer layer and said barrierlayer and is located between said outer layer and said barrier layer;wherein said at least one tie layer, independently, comprises apolyacrylate or a polymethacrylate wherein the ester portion thereof hasfrom 1 to about 12 carbon atoms, or a blend of said polyacrylate or saidpolymethacrylate with a polyolefin; a polyanhydride or a polymaleicanhydride; or a copolymer of said polyanhydride or said polymaleicanhydride with an olefin, with ethylvinylacetate, or with ethyleneacrylate; wherein said laminate has an H₂S transmission rate of lessthan about 200 cc/100 m²/day; and wherein said VCI is capable ofevaporating and filling said closed space.
 2. The corrosive gasresistant laminate of claim 1, wherein said outer layer comprises apolyolefin or a copolymer thereof; a copolymer of ethylene-ethylacrylateor ethylene-methylacrylate; a polymer derived from a diene, or acopolymer derived from a diene; polystyrene; a halocarbon containingpolymer; a heterochain thermoplastic; a polysulfide; a polyphthalamide;a polyurethane; a polyamide; a polyester; or any combination of thepreceding; wherein said corrosive gas resistant barrier layer comprisesa polyvinyl alcohol or an alkylene-vinyl alcohol copolymer, or a blendof either with another polymer; or a carbon monoxide-containing ethylenepolymer blended with said polyvinyl alcohol polymer or saidpolyalkylene-vinyl alcohol copolymer; a polyamide, or a polyamidecopolymer, or a blend of either with another polymer; a polyvinylacetatepolymer, or a polyvinylacetate copolymer, or blend of either withanother polymer; or a polyvinylidene chloride, or a copolymer thereof.3. The corrosive gas resistant laminate of claim 1, wherein said outerlayer polymer comprises polyethylene including various low and highdensity polyethylenes, polypropylene, and copolymers thereof, anethylene-ethyl acrylate copolymer, an ethylene methyl acrylatecopolymer, a copolymer of acrylonitrile-butadiene-styrene (ABS), acopolymer of methyl methacrylate-styrene, polybutyldiene,polychloroprene, a copolymer of butadiene and styrene,polychlorotrifluoroethylene, polytetrafluoroethylene, a fluorinatedethylene polypropylene copolymer, polyvinylchloride, polyvinylidenechloride, polyvinylidene fluoride, a blend of polyethylene andpolytetrafluoroethylene, a copolymer of melamine formaldehyde, apolyurethane, a polyamide, or a polyester, or any combination thereof;wherein said VCI is a triazole or a derivative thereof; a benzoate or asalt of benzoic acid; a carbonate; a phosphate; an alkali metalmolybdate, a dimolybdate, an amine molybdate, or a salt thereof; analkali dibasic acid salt; an organic nitrite, or an alkali metalnitrite; at least one C₆ to C₁₂ aliphatic monocarboxylic acid, at leastone C₆ to C₁₂ aliphatic dicarboxylic acid, or at least one primaryaromatic amide; or any combination of the preceding; wherein the amountof said VCI is from about 0.25 to about 10 parts by weight for every 100parts by weight of said outer layer; wherein said tie layer comprisessaid acrylate or said methacrylate blended with a polyolefin; saidpolymeric anhydride or said polymaleic anhydride; or said copolymer ofsaid polymeric anhydride or of said polymaleic anhydride with either anolefin or with an ethyl-vinyl acetate; or any combination of thepreceding; wherein said corrosive gas resistant barrier layer comprisesa polyvinyl alcohol or an alkylene-vinyl alcohol copolymer, or a blendof either with another polymer; or a carbon monoxide-containing ethylenepolymer blended with said polyvinyl alcohol polymer or saidpolyalkylene-vinyl alcohol copolymer; a polyamide, or a polyamidecopolymer, or a blend of either with another polymer; a polyvinylacetatepolymer, or a polyvinylacetate copolymer, or blend of either withanother polymer; or a polyvinylidene chloride, or a copolymer thereof.4. The corrosive gas resistant laminate of claim 3, wherein saidlaminate has an oxygen transmission rate of less than about 50 cc/100m²/day.
 5. The corrosive gas resistant laminate of claim 3, wherein saidVCI is benzotriazole, tolytriazole, ammonium benzoate,cyclohexylammonium benzoate, said salt of benzoic acid, said alkalimetal molybdate, said dimolybdate, an aliphatic or aromatic amine saltmolybdate having a total of from about 3 to about 30 carbon atoms, orsaid alkali metal nitrite; or any combination thereof; wherein saidcorrosive gas resistant barrier layer polymer contains a phenoladditive; and wherein said laminate has an H₂S transmission rate of lessthan about 100 cc/100 m²/day.
 6. The corrosive gas resistant laminate ofclaim 5, wherein said outer layer comprises said polyethylene, saidpolyester, or said polyamide, or any combination thereof; wherein saidVCI is said alkali metal nitrite and wherein the amount of said nitriteis from about 0.4 to about 3.0 parts by weight per 100 parts by weightof said outer layer; wherein said tie layer is said polymeric anhydride,an ethylene-maleic anhydride copolymer, or a copolymer ofpropylene-maleic anhydride, or any combination thereof; wherein saidcorrosive gas resistant barrier layer is a copolymer of saidethylene-vinyl alcohol wherein the amount of ethylene in said copolymeris from about 30 to about 45 mole percent; or said polyvinylidenechloride, or a copolymer thereof with vinyl chloride, acrylate, oracrylonitrile; wherein said corrosive gas resistant barrier layer phenoladditive is 2-hydroxy-4-octoxybenzophenone,2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, octyl3-(3′,5′-di-t-butyl-4-hydroxy)phenyl propionate, 2(2′-hydroxy-3′,5′di-tert-amyl)phenyl-benzotriazole, tertiary butyl salicylate,butylhydroquinone, or any combination thereof, and wherein the amount ofsaid phenol is from about 0.7 to about 5 parts by weight per 100 totalparts by weight of said barrier layer; and wherein the total thicknessof said at least one or more outer polymer layers is from about 65 toabout 93%, wherein the total thickness of said at least one or more tielayers is from about 3 to about 20%, and wherein the total thickness ofsaid at least one or more corrosive barrier layers is from about 2 toabout 15% based upon the total thickness (100%) of said corrosive gasresistant laminate.
 7. A corrosive gas resistant laminate, comprising: alaminate capable of wrapping and forming a closed space about a metalsurface and preventing metal corrosive gases comprising H₂S, SO₂, andhalogen gases from corroding said metal surface, and wherein saidlaminate is not utilizable as a food wrap; said laminate comprising: atleast one corrosive gas resistant barrier layer; at least one outerlayer, said outer layer having at least one tie layer compound blendedtherein that is compatible with said outer layer material and saidbarrier layer; wherein said each tie layer compound, independently,comprises a polyacrylate or a polymethacrylate wherein the ester portionthereof has from 1 to about 12 carbon atoms, or a blend of saidpolyacrylate or said polymethacrylate with a polyolefin; a polyanhydrideor a polymaleic anhydride; or a copolymer of said polyanhydride or saidpolymaleic anhydride with an olefin, with ethylvinylacetate, or withethylene acrylate; wherein said laminate has an H₂S transmission rate ofless than about 200 cc/100 m²/day; and including at least one VCIcompound in said outer layer, and wherein said VCI is capable ofevaporating and filling said closed space.
 8. The corrosive gasresistant laminate of claim 7, wherein said outer layer comprises apolyolefin or a copolymer thereof; a copolymer of ethylene-ethylacrylateor ethylene-methylacrylate; a polymer derived from a diene, or acopolymer derived from a diene; polystyrene; a halocarbon containingpolymer; a heterochain thermoplastic; a polysulfide, a polyphthalamide;a polyurethane; a polyamide; a polyester, or any combination of thepreceding; and wherein said corrosive gas resistant barrier layercomprises said polyvinyl alcohol or an alkylene-vinyl alcohol copolymer,or a blend of either with another polymer, or a carbonmonoxide-containing ethylene polymer blended with said polyvinyl alcoholpolymer or said polyalkylene-vinyl alcohol copolymer, a polyamide, or apolyamide copolymer, or a blend of either with another polymer; apolyvinylacetate polymer or a polyvinylacetate copolymer, or blend ofeither with another polymer; or a polyvinylidene chloride, or acopolymer thereof.
 9. The corrosive gas resistant laminate of claim 8,wherein said outer layer comprises a polyethylene, said polyester, orsaid polyamide, or any combination thereof; wherein said outer layer tiecompound is said polymeric anhydride, an ethylene-maleic anhydridecopolymer, or a copolymer of propylene maleic-anhydride, or anycombination thereof; wherein said corrosive gas resistant barrierlaminate is a copolymer of ethylene-vinyl alcohol wherein the amount ofethylene in said copolymer is from about 30 to about 45 mole percent;wherein said VCI is benzotriazole, tolytriazole, ammonium benzoate,cyclohexylammonium benzoate, a salt of benzoic acid, an alkali metalmolybdate, a dimolybdate, an aliphatic or aromatic amine salt molybdatehaving a total of from about 3 to about 30 carbon atoms, or an alkalimetal nitrite; or any combination thereof; and wherein said laminate hasan oxygen transmission rate of less than about 50 cc/100 m²/day.
 10. Thecorrosive gas resistant laminate of claim 8, including at least oneinner layer, said inner layer having at least one tie layer compoundblended therein that is compatible with said inner layer material andsaid barrier layer material; wherein said inner layer comprises apolyolefin or a copolymer thereof; a copolymer of ethylene-ethylacrylateor ethylene-methylacrylate; a polymer derived from a diene, or acopolymer derived from a diene; polystyrene; a halocarbon polymer; aheterochain thermoplastic; a polysulfide; a polyphthalamide; apolyurethane; a polyimide; a polyester; or any combination of thepreceding; wherein said inner layer tie compound independently comprisesa polyacrylate or a polymethacrylate wherein the ester portion thereofhas from 1 to about 12 carbon atoms, or a blend of said polyacrylate orsaid polymethacrylate with a polyolefin; a polyanhydride or a polymaleicanhydride; or a copolymer of said polyanhydride or said polymaleicanhydride with an olefin, with ethylvinylacetate, or with ethyleneacrylate; and wherein said inner layer contains at least one VCIcompound therein.
 11. The corrosive gas resistant laminate of claim 10,wherein said outer layer is free of any VCI compound, wherein said,inner layer comprises a polyethylene, said polyester, or said polyamide,or any combination thereof; wherein said inner layer tie compound issaid polymeric anhydride, an ethylene-maleic anhydride copolymer, or acopolymer of propylene maleic anhydride, or any combination thereof;wherein said inner layer VCI compound is benzotriazole, tolytriazole,ammonium benzoate, cyclohexylammonium benzoate, a salt of benzoic acid,an alkali metal molybdate, a dimolybdate, an aliphatic or aromatic aminesalt molybdate having a total of from about 3 to about 30 carbon atoms,or an alkali metal nitrite; or any combination thereof; wherein thetotal thickness of said at least one or more outer polymer layers and/orsaid one or more polymer inner layers including any tie layer compoundtherein is from about 75% to about 98%, and wherein the total thicknessof said one or more corrosive barrier layers is from about 2% to about25% based upon the total thickness (100%) of said corrosive gasresistant laminate; and wherein said corrosive gas resistant barrierlayer polymer is said polyvinyl alcohol, a copolymer of ethylene-vinylalcohol, said polyamide, said carbon monoxide-containing ethylenepolymer blended with said polyvinyl alcohol or said polyvinyl alcoholcopolymer; said polyvinylidene chloride or said polyvinlidene copolymer,or any combination thereof.
 12. The corrosive gas resistant laminate ofclaim 9, wherein said VCI compound is said alkali metal nitrite andwherein the amount of said nitrite is from about 0.4 to about 3.0 partsby weight per 100 parts by weight of said inner layer.
 13. The corrosivegas resistant laminate of claim 11, wherein said VCI is said alkalimetal nitrite and wherein the amount of said nitrite is from about 0.4to about 3.0 parts by weight per 100 parts by weight of said outerlayer.
 14. A corrosive gas resistant laminate for protecting metalagainst corrosion, comprising: a laminate capable of wrapping andforming a closed space about a metal surface and preventing metalcorrosive gases comprising H₂S, SO₂, and halogen gases from corrodingsaid metal surface, and wherein said laminate is not utilizable as afood wrap; said laminate comprising: at least one outer layer that is acorrosive gas resistant barrier layer; at least inner layer comprising aVCI; at least one tie layer that is compatible with said outer barrierlayer and said inner layer; and wherein each said tie layer,independently, comprises a polyacrylate or a polymethacrylate whereinthe ester portion thereof has from 1 to about 12 carbon atoms, or ablend of said polyacrylate or said polymethacrylate with a polyolefin; apolyanhydride or a polymaleic anhydride; or a copolymer of saidpolyanhydride or said polymaleic anhydride with an olefin, withethylvinylacetate, or with ethylene acrylate; wherein said laminate hasan H₂S transmission rate of less than about 200 cc/100 m²/day; andwherein said VCI is capable of evaporating and filling said closedspace.
 15. The corrosive gas resistant laminate of claim 14, whereinsaid corrosive gas resistant barrier layer comprises a polyvinyl alcoholor an alkylene-vinyl alcohol copolymer, or a blend of either withanother polymer; or a carbon monoxide-containing ethylene polymerblended with said polyvinyl alcohol polymer or said polyalkylene-vinylalcohol copolymer; a polyamide, or a polyamide copolymer, or a blend ofeither with another polymer; a polyvinylacetate polymer, or apolyvinylacetate copolymer, or blend of either with another polymer; ora polyvinylidene chloride, or a copolymer thereof.
 16. The corrosive gasresistant laminate of claim 15, wherein said corrosive gas resistantbarrier layer polymer is said polyvinyl alcohol, a copolymer ofethylene-vinylalcohol, said polyamide, said carbon monoxide-containingethylene polymer blended with said polyvinyl alcohol or said polyvinylalcohol copolymer; said polyvinylidene chloride or said polyvinylidenecopolymer, or any combination thereof; wherein said inner polymer layercomprises polyethylene including various low and high densitypolyethylenes, polypropylene, and copolymers thereof, an ethylene-ethylacrylate copolymer, an ethylene methyl acrylate copolymer, a copolymerof acrylonitrile-butadiene-styrene (ABS), a copolymer of methylmethacrylate-styrene, polybutyldiene, polychloroprene, a copolymer ofbutadiene and styrene, polychlorotrifluoroethylene,polytetrafluoroethylene, a fluorinated ethylene polypropylene copolymer,polyvinylchloride, polyvinylidene chloride, polyvinylidene fluoride, ablend of polyethylene and polytetrafluoroethylene, a copolymer ofmelamine formaldehyde, a polyurethane, a polyamide, or a polyester, orany combination thereof; wherein said VCI is a triazole or a derivativethereof; a benzoate or a salt of benzoic acid; a carbonate; a phosphate;an alkali metal molybdate, a dimolybdate, an amine molybdate, or a saltthereof; an alkali dibasic acid salt; an organic nitrite, or an alkalimetal nitrite; at least one C₆ to C₁₂ aliphatic monocarboxylic acid, atleast one C₆ to C₁₂ aliphatic dicarboxylic acid, or at least one primaryaromatic amide; or any combination of the preceding; wherein the amountof said VCI is from about 0.25 to about 10 parts by weight for every 100parts by weight of said outer layer; and wherein said tie layercomprises said acrylate or said methacrylate blended with an polyolefin;said polymeric anhydride or said polymaleic anhydride; or said copolymerof said polymeric anhydride or of said polymaleic anhydride with eitheran olefin or with an ethyl-vinyl acetate; or any combination of thepreceding.
 17. The corrosive gas resistant laminate of claim 16, whereinsaid corrosive gas resistant barrier layer is a copolymer of saidethylene-vinyl alcohol wherein the amount of ethylene in said copolymeris from about 30 to about 45 mole percent; or said polyvinylidenechloride, or a copolymer thereof with vinyl chloride, an acrylate, oracrylonitrile; wherein said inner layer comprises said polyethylene,said polyester, or said polyamide, or any combination thereof, whereinsaid inner layer VCI is benzotriazole, tolytriazole, ammonium benzoate,cyclohexylammonium benzoate, a salt of benzoic acid, an alkali metalmolybdate, said dimolybdate, an aliphatic or aromatic amine saltmolybdate having a total of from about 3 to about 30 carbon atoms, orsaid alkali metal nitrite; or any combination thereof; wherein said tielayer is located between said outer corrosion gas resistant barrierlayer and said inner polymer layer, and wherein said tie layer is saidpolymeric anhydride, an ethylene-maleic anhydride copolymer, or acopolymer or a copolymer of propylene maleic anhydride, or anycombination thereof; and wherein said laminate has an H₂S transmissionrate of less than about 100 cc/100 m²/day.
 18. The corrosive gasresistant laminate of claim 17, wherein the total thickness of said atleast one or more corrosion gas resistant barrier layers is from about 2to 15%, wherein the total thickness of said one or more inner polymerlayers is from about 65 to about 93%, and wherein the total thickness ofsaid one or more tie layers is from about 3 to about 20% based upon thetotal thickness (100%) of said corrosive gas resistant laminate.